Ultrasonography cervical volume as a predictor of successful induction of labor: a systematic review and meta-analysis

Aim. To compare the cervical volume of patients who underwent successful and failed induction of labor (IOL) procedures.

Materials and methods. This systematic review and meta-analysis were conducted according to PRISMA guidelines. A comprehensive literature search was performed in PubMed, EMBASE, Scopus, and Google Scholar to identify cohort studies published between January 01, 2005 and December 31, 2024, that compared cervical volume in pregnant women who underwent IOL. A random-effects meta-analysis was performed.

Results. Seven studies involving 534 pregnant women were included. Four studies were considered low risk of bias and two studies were regarded as high risk of bias. Risk of bias assessment could not be performed in one study because the full-text of the article was not available. The pooled analysis of two studies involving 168 pregnant women demonstrated a positive association between the lower cervical volume and successful vaginal delivery within 24 hours (odds ratio 7.19; 95% confidence interval: 3.31 to 15.64; I²  = 0%). The pooled analysis of five studies involving 422 pregnant women showed no statistically significant difference between successful and failed IOL, with a mean difference –1.32 cm³; 95% confidence interval: –8.37 to 5.72; I²  = 89.8%). Subgroup analyses showed no statistically significant association between cervical volume and successful IOL when defined as vaginal delivery without time restriction or within 24 hours. However, a significantly lower cervical volume was observed in women who achieved the active phase of labor within 12 hours. The Egger’s regression test confirmed the absence of small‑study effects (coefficient = 0.50, standard error = 1.75, p = 0.78).

Conclusion. Cervical volume has significant potential as a parameter for predicting successful IOL, with a smaller cervical volume being associated with better outcomes, although subgroup findings remain inconsistent.

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